Due to an increase in data communication demand, optical signal modulation technology for enabling the transmission of a large volume of traffic and optical transmission networks using optical signal multiplexing technology are becoming widespread. In particular, 100 Gigabit Ethernet (GbE) LR-4 (long range) that is one scheme of Ethernet (registered trademark) is known as a high-speed optical transmission technology for a short distance. A transmission scheme in 100 GbE LR-4 uses multi-channel optical transmission in which a data transmission of 100 Gbps (bps: bits per second) is performed by using optical signals having a plurality of different wavelengths. For example, in 100 GbE LR-4, a data transmission of 100 Gbps is implemented by performing a data transmission of 25 Gbps on each of four wavelengths (each wavelength is referred to as a channel). The majority of schemes using a wavelength of a 1.3 μm band are used in Ethernet (registered trademark) and the 1.3 μm band is also used in 100 GbE LR-4. Because a zero-dispersion wavelength of a single-mode fiber is approximately 1.3 μm, there is an advantage that it is not necessary to consider waveform degradation due to wavelength dispersion in optical transmission using the 1.3 μm band.